1. Field of Invention
The invention relates to ballasts for gas discharge lamps, particularly of a kind having means to permit the power supplied to the lamps to be adjusted by timed connection/disconnection of the ballast with/from its source of power.
2. Elements of Prior Art
It is well known that significant improvements in overall cost-effectivity of the lighting function can result from appropriately controlling the level of light output from lighting fixtures used for general lighting in offices and the like.
Fluorescent lamp ballasting systems adapted to permit control of light output level on a systems basis presently do exist--as for instance in accordance with U.S. Pat. Nos. 4,207,498 and 4,350,935 to Spira et al.
However, there are significant complexities associated with practical applications of such light level control systems; and, in spite of the very significant improvements potentially available in overall lighting efficacy, such light control systems have not gained wide acceptance.
3. Inventive Rationale
A significant part of the value available from a light control system may be attained by simply permitting the light level to be readily adjustable between a normal brightness level and a reduced brightness level.
However, to make this kind of approach commercially attractive, it must be very simple to install and use; and it must not represent a significant cost-penalty.
For instance, if--perhaps by the use of some special electronic ballasts in the lighting fixtures--it were to be possible just to flick the light switch OFF and ON again in order to establish a reduced light level, no special light dimmers would be needed, and no special wiring would be required.